Undesired weight loss, particularly lean mass loss is a relatively common occurrence in critical illness, and has a significant impact on morbidity and mortality. This is particularly true in cancer patients, where such mass losses can become treatment-limiting, and thus impact overall prognosis.
Cachexia is a syndrome characterized by anorexia, weight loss, premature satiety, asthenia, loss of lean body mass, and multiple organ dysfunction. It is a common consequence of chronic illnesses (both malignant and non-malignant) and is associated with a poorer prognosis in chronic obstructive pulmonary disease (COPD), chronic heart failure (CHF), renal failure, AIDS, dementia, chronic liver disease and cancer. It is often independent of other indicators of disease severity. (Witte, K. K. A. and Clark, A. L.: Nutritional abnormalities contributing to cachexia in chronic illness, International Journal of Cardiology 85:23-31, 2002)
Pulmonary disease is often associated with cachexia, and substantial numbers of patients suffering from COPD, particularly emphysema, become emaciated during the course of the disease. Weight loss is an independent risk factor for prognosis, and is often associated with increased oxygen consumption. COPD is also associated with a general elevated systemic inflammatory response, reflected by elevated concentrations of pro-inflammatory cytokines and acute phase proteins in the peripheral blood. Such changes are often associated with muscle wasting syndromes.
Studies with incubated muscles and muscle extracts suggest that the ATP-dependent ubiquitin-proteosome pathway is responsible for most of the increased proteolysis which ultimately results in muscle wasting. In particular, increased levels of ubiquitin-conjugated proteins, and increases in mRNA levels for polyubiquitin, certain proteosome subunits and the ubiquitin-conjugating enzyme E214K are features found in most atrophying muscles.
The majority of patients with cancer whose disease progresses to metastatic disease develop cachexia during their treatment program and the cachexia contributes to their deaths. The frequency of weight loss in cancer patients ranges from 40% for patients with breast cancer, acute myelocytic leukemia, and sarcoma to more than 80% in patients with carcinoma of the pancreas and stomach. About 60% of patients with carcinomas of the lung, colon or prostate have experienced weight loss prior to beginning chemotherapy. Although the relationship between pretreatment malnutrition (weight loss) and adverse outcome is established, no consistent relationship has been demonstrated between the development of cachexia and tumor size, disease stage, and type or duration of the malignancy.
Cancer cachexia is not simply a local effect of the tumor. Alterations in protein, fat, and carbohydrate metabolism occur commonly. For example, abnormalities in carbohydrate metabolism include increased rates of total glucose turnover, increased hepatic gluconeogenesis, glucose intolerance and elevated glucose levels. Increased lipolysis, increased free fatty acid and glycerol turnover, hyperlipidemia, and reduced lipoprotein lipase activity are frequently noted. The weight loss associated with cancer cachexia is caused not only by a reduction in body fat stores but also by a reduction in total body protein mass, with extensive skeletal muscle wasting. Increased protein turnover and poorly regulated amino acid oxidation may also be important. The presence of host-derived factors produced in response to the cancer have been implicated as causative agents of cachexia, e.g., tumor necrosis factor-α (TNF) or cachectin, interleukin-1 (IL-1), IL-6, gamma-interferon (IFN), and prostaglandins (PGs) (e.g., PGE2).
Weight loss is common in patients with carcinomas of the lung and gastrointestinal tract, resulting in a massive loss of both body fat and muscle protein, while non-muscle protein remains unaffected. While loss of body fat is important in terms of energy reserves, it is loss of skeletal muscle protein that results in immobility, and eventually impairment of respiratory muscle function, leading to death from hypostatic pneumonia. Although cachexia is frequently accompanied by anorexia, nutritional supplementation alone is unable to maintain stable body weight and any weight that is gained is due to an increase in adipose tissue and water rather than lean body mass. The same is true for appetite stimulants, such as megestrol acetate and medroxyprogesterone acetate, suggesting that loss of lean body mass is due to factors other than energy insufficiency.
Skeletal muscle mass is a balance between the rate of protein synthesis and the rate of degradation. Patients with cancer cachexia show a depression of protein synthesis in skeletal muscle and an increase in protein degradation, which is reflected in an increased expression of the ubiquitin-proteasome proteolytic pathway, the major determinant of protein degradation. Thus skeletal muscle from cachectic cancer patients shows increased expression of mRNA for both ubiquitin and proteasome subunits, while proteasome proteolytic activity increased in parallel with ubiquitin expression. The inability of anabolic stimuli to increase lean body mass in cachectic patients suggests that protein degradation must be attenuated before muscle mass can increase. Eicosapentaenoic acid (EPA), downregulates the increased expression of the ubiquitin-proteasome proteolytic pathway in the skeletal muscle of cachectic mice, and has been shown to stabilize body weight in cachectic patients with pancreatic cancer. When patients consumed an energy-dense supplement containing 32 g protein and 2 g EPA body weight increased and this was attributed solely to an increase in lean body mass (Barber, M. D., Ross, J. A., Voss, A. C., Tisdale, M. J., Fearon, K. C. H. The effect of an oral nutritional supplement enriched with fish oil on weight-loss in patients with pancreatic cancer. Br. J. Cancer, 81: 80-86, 1999).
A recent study by May et al (May, P. E., Barber, A., D'Olimpio, J. T., Hourihane, A. and Abumrad, N. N. Reversal of cancer-related wasting using oral supplementation with a combination of β-hydroxy-β-methylbutyrate, arginine and glutamine. Am. J. Surg., 183: 471-479, 2002) showed a mixture of HMB, arginine and glutamine to be effective in increasing body weight in weight losing patients with advanced (stage IV) cancer. Moreover, the increase in body weight was attributed to an increase in fat-free mass, as observed with EPA.
The use of the polyunsaturated fatty acid eicosapentaenoic acid is suggested for the treatment of cachexia by inhibiting lipolytic activity of lipolytic agents in body fluids and the activity of the enzyme guanidino-benzoatase. See Tisdale, M. J., and Beck, A., U.S. Pat. No. 5,457,130, issued Oct. 10, 1995; and Tisdale, et al. Cancer Research 50: 5022-5026 (August 1990). However, the product taught by Tisdale was in a solid dosage form, requiring an already ill patient to swallow 12-16 capsules per day. This method had serious drawbacks, including difficulty in swallowing, belching, and bad odor.
HMB has been found to be useful within the context of a variety of applications. Specifically, in U.S. Pat. No. 6,031,000 to Nissen et al. describes a composition comprising HMB, free L-arginine, and free L-glutamine. This patent also provides a method for the treatment of disease-associated wasting of an animal and other methods comprising administering to the animal a composition comprising HMB and at least one free amino acid.
U.S. Pat. No. 5,348,979 to Nissen et al. describes the use of HMB in the nitrogen retention in human subjects. The amount of HMB administered is effective to conserve protein as determined by reduction in urinary nitrogen. The method can be used with patients having a negative nitrogen balance due to disease conditions, and also with normal elderly persons who are subject to protein loss.
U.S. Pat. No. 5,028,440 to Nissen describes a method for raising meat producing domestic animals to increase lean tissue development. HMB is fed within the range of from 0.5 to 100 mg.
U.S. Pat. No. 4,992,470 to Nissen describes the use of HMB to be markedly more effective for activating the immune function of T lymphocytes of mammals than .alpha.-ketoisocaproate (KIC). For activation of the T lymphocytes, HMB or an edible water-soluble salt thereof is administered to the mammal by a route through which the HMB enters the blood of the mammal. The amount administered is sufficient for effective enhancement of the blastogenesis of their T lymphocytes.
Some bodybuilding advertising claims make the bare assertion that HMB promotes protein synthesis, (see, e.g. websites:
http://www.bodybuilding.com/store/kzn/hmb.html;
http://www.interactivenutrition.com/products/hmb.php; and
http://www.interactivenutrition.com/learningzone/hmb.php)
but these lack any scientific documentation and amount to mere “puffery” that appears to misstate the established inhibitory effect of HMB protein degradation, which also leads to gain in muscle mass but is not “synthesis”. The only scientific study making this suggestion is a 1996 abstract by Ostaszewski, et al (J. Anim. Sci 1996; 74(Supppl. 1)); which claims their data in rats and chicks indicates that “HMB stimulates [protein synthesis] slightly (avg. 6%) and markedly decreased [protein breakdown] (avg. −18%)”. A later paper by 4 of the same authors using the same model in rats and chicks faled to repeat the synthesis effect and concludes that “HMB had no significant effect on protein synthesis” (Ostaszewski, et al (J. Anim. Physiol. a. Anim. Nutr. 84 (2000), 1-8). This leaves doubt and uncertainty about whether HMB stimulates protein synthesis or not, but in any event, each of these authors reports on normal subjects; not one addresses the effect of HMB in individuals whose muscle status is compromised by a disease-associated wasting condition. In such conditions, protein synthesis is significantly depressed.
German patent DE 29707308 to Kunz describes the use of branched chain amino acids in combination with HMB to promote muscle generation in the weight training population. Kunz teaches that a supplement of 3 gm taken daily with a protein consumption of 200 gm per day enhances the value of nutritional protein and significantly increases the protein efficiency. Kunz also teaches that better effects can be achieved when HMB is combined with protein hydrolysates and/or free amino acid mixtures rather than with intact (pure) proteins.
U.S. Pat. No. 5,976,550 to Engel et al. describes a dietary food supplement for weight reduction formed of a mixture of a sugar based confectionary containing therapeutic amounts of chitosan, kava and a fat burning nutriceutical which may include choline/inusital, chromium picolinate, HMB, carnitine and pyruvate. The nutriceutical ingredient mixed with the chitosan and kava functions to burn whatever fat the body has consumed, i.e. to metabolize better any fat that is ingested and not attracted to the chitosan.
Commercial products designed for the weight lifting population that contain HMB include Lean DynamX by EAS Inc. of Golden, Colo. Lean DynamX provides a blend of ingredients that support fat loss without the use of strong stimulants. The ingredients include HMB, chromium picolinate, conjugated linoleic acid, mate leaves and stems and carnitine tartrate. The powder composition is mixed with water and taken 2-3 servings daily, with one serving taken 30 minutes before workouts.
Additional commercial products include Mega HMB Fuel® from Twinlab Corporation in Hauppauge, N.Y. Mega HMB Fuel® contains 750 mg of HMB in one capsule. The suggested daily dosage is 4 capsules to support damage to muscle cells which can occur subsequent to intense resistance exercise.
Also of interest is U.S. Pat. No. 5,444,054 to Garleb, et al. and related U.S. Pat. Nos. 5,780,451 and 6,468,987. These documents describe compositions and methods useful in the treatment of ulcerative colitis. Such compositions include a protein source that can be intact or hydrolyzed proteins of high biological value (col. 21); an indigestible oligosaccharide such as fructooligosaccharide; and a lipid blend containing a relatively high proportion of eicosapentaneoic acid, which contributes to a relatively high ω-3 to ω-6 fatty acid ratio.
Long chain fatty acid bio-pathways and physiological actions are discussed in U.S. Pat. No. 5,223,285 to DeMichele, et al., the entirety of which is incorporated herein by reference.
The prevention and/or treatment of cachexia remain a frustrating problem. Both animal and human studies suggest that nutritional support is largely ineffective in repleting lean body mass in the cancer-bearing host. Randomized trials exploring the usefulness of total parenteral nutrition (TPN) support as an adjunct to cytotoxic antineoplastic therapy have demonstrated little improvement in treatment results. See for example Brennan, M. F., and Burt, M. E., 1981, Cancer Treatment Reports 65 (Suppl. 5): 67-68. This, along with a clear demonstration that TPN can stimulate tumor growth in animals suggests the routine use of TPN in cancer treatment is not justified. Kisner, D. L., 1981, Cancer Treatment Reports 65 (Suppl. 5): 1-2.